Extraction of lube oil with phenol up to haze point change



May 16, 1961 R. F. BURKE ET AL 2,984,616

EXTRACTION OF LUBE OIL WITH PHENOL UP TO HAZE POINT CHANGE Filed Oct. 27, 1958 2 Sheets-Sheet 1 :0 l m o T- Z 3 E o a.

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EXTRACTION OF LUBE OIL WITH PHENOL UP TO HAZE POINT CHANGE Filed Oct. 27, 1958 2 Sheets-Sheet 2 HYDRO-ISOMERIZATION ZONE I2\\ HIGH V.l. RAFFINATE PRODUCT 26 20\ 4 BEEND PHENOL f f 22 DISTILLATION l6 1 UNIT 2 EXTRACTION DISTLLLATE ZONE l5 CRUDE +9 EXTRAcT .|9 25 FIGURE 2 Robert F Burke Bur/0n J Sufker WVENTORS B) "H ES. B -11 405m United States Patent EXTRACTION 0F LUBE OIL WITH PHENOL UP TO HAZE POINT CHANGE Robert F. Burke, Summit, and Burton J. Sutker, Newark,

N.J., assignors to Esso Research and Engineering 'Company, a corporation of Delaware Filed Oct. 27, 1958, Ser. No. 769,732

9 Claims. (Cl. 208-87) The present invention is concerned with the production of lube oil products having improved stability characteristics. More specifically, it deals with the manufacture of lube products having a decreased tendency to form a haze with the passage of time.

It is well known in the art to form various lubricating oils, commonly referred to as lubes, from hydrocarbon fractions derived from petroleum crudes. With particular regards to the relatively inexpensive lube oils, a common procedure known in the art is to extract these hydrocarbon fractions with phenol so as to give a rafinate (lube oil product) of high viscosity index, e.g. 75 or greater. A high viscosity index lube oil product is desired since such a material resists changes in viscosity with changes in temperature and thus may be used under varying conditions in motors, machines, etc. It is particularly desired when producing a low cold test lube, i.e. a lube oil having a low pour point and designed to be used at low temperature conditions, since excessive thickening at low temperatures (low viscosity index) is quite unacceptable in such a product.

In addition to having a high viscosity index, the lube oil product must satisfy other consumer standards, among these the degree of haze formation in the lube oil. Although low cold test lubes are normally made from naphthenic crude sources especially selected for their low wax content, a haze will tend to form due to the precipitation of small quantities of wax crystals within the lube product.

Heretofore, it has been standard practice to set a cloud point requirement in accordance with the ASTM cloud point test, the ASTM cloud point being designed to fix the temperature at which the Wax first starts to precipitate within the lube. Though well known in the art, briefly the ASTM cloud point test is performed as follows:

The oil is heated at least 25 F. above the approximate cloud point and the clear oil is poured in a standard glass tube to a height of 2 to 2%". The tube is stoppered and a thermometer runs through the stopper into the oil. The oil is cooled by placing the tube in a cooling mixture.

,The cooling mixture is changed at designated temperature levels so that the cooling rate is fairly uniform. Oil is inspected at each multiple of 2 F. until a distinct cloud or haziness appears. This temperature is the ASTM cloud point.

However, it has been observed that lubes, particularly low cold test lubes, will often precipitate after a length of time at temperatures considerably above their ASTM cloud point rating. Such lubricants of course meet with poor consumer acceptance and are undesirable even though they initially satisfied ASTM cloud point requirements. 7

One method of preventing this haze formation in lubes is to dewax the lube product by the use of an appropriate solvent and chilling. However, this process is expensive and is generally economically impractical as applied to low-priced lube oils. Thus there is a need in the art for an inexpensive process capable of producing a high viscosity index lube having a low haze-forming propensity, particularly a lube also having a low pour point.

The present invention satisfies this need. It has now been found that, in contrast to prior art procedures, it is undesirable to perform phenol extraction to maximize the viscosity index of the raffinite. Rather, in accordance with the present teachings, a mild phenol extraction step in combination with isomerization of the rafiinate yields a lube of high viscosity index and relatively low haze temperature. The term haze temperature is herein employed to designate the true or equilibrium cloud point as opposed to the ASTM cloud point. The haze temperature thus is the lowest temperature at which a sample can be stored indefinitely without becoming hazy. In more specific terms, the present invention teaches that a hydrocarbon oil be subjected to a mild phenol extraction so as to give a raffinate of an intermediate (less than that ultimately desired) viscosity index, e.g. 65 or less, the intermediate viscosity index being within the range found to give substantially constant haze point. The rafiinate is then subjected to hydro-isomerization (isomerization in the presence of hydrogen) which results in further increasing viscosity index to or more while not adversely affecting the haze point properties to any appreciable degree, as would have been the case if a more severe phenol extraction had been utilized. Additionally, the isomerization yields a low pour point product finding demand as, for example, low cold test lubes for industrial oils and for making white oils. In one embodiment of the present invention, the high viscosity index product of the isomerization step is blended with a minor portion, i.e. less than 5 wt. percent, of the heavy constituents of the phenol extract, these heavy constituents acting as anti-oxidants and wax solubilizers'.

By use of the present combination process, a lube of high viscosity index and oxygen stability, as well as low pour and haze point, is secured in an economical manner.

The various aspects and modifications of the present invention will be made more clearly apparent by reference to the following description, example and accompanying drawings.

Figure 1 depicts the variation of haze point with the viscosity index of the rafiinate of a phenol extraction step.

Figure 2 illustrates the present combination of process steps yielding an improved lube product.

Prior to describing the process aspects of the present invention, the methods of accurately determining the haze point, i.e. equilibrium cloud point, will be described. Two test procedures, designated straight haze and diluted haze tests, were employed and were found to give substantially the same results.

In the straight haze test, a series of constant temperature baths are set up at 10 F. intervals (such as 35, 45, 55, 65 F). Samples, in glass bottles are inserted in each bath and examined daily. After 14 days, the temperature midway between the highest temperature at which the sample appears cloudy and the lowest temperature at which the sample remains clear is reported as the haze point.

The diluted haze test is similar except that the sample is diluted with 3 parts of a 75% methyl ethyl ketone solution in toluene. The diluted samples are then placed in baths and examined at hourly intervals for the first 7 hours and then daily. Due to the very poor solvency of methyl ethyl ketone for wax, less time (usually less than 3 days) is normally required to reach equilbrium when employing this test.

Referring now to Figure 1, shown therein is a plot of haze point (as determined by the above procedures) versus the viscosity. index of the raffinate product of phenol extracting a typical distillate of a Tia Juana 102 crude (a naphthenic crude). The distillate had a boiling point of about 800 to 1050* F., and a viscosity index of about 36. The extractions were performed at a temperature of about 150 to 200 F., using 150 to 300 vol. percent phenol based on feed. The phenol contained 5-10% water.

The ASTM cloud point of the rawdistillate was 40 F. below the haze point. Rerunning this distillate to 95% overhead lowered the ASTM cloud point even more but did not change the haze .point which remained constant at about 40 F. Comparing the upper line which represents the haze point, and the lower line representing ASTM cloud point, it is seen that the haze point was consistently higher, thus indicating the failure of ASTM cloud point to determine the temperature at which a lube product would not give rise to haze upon standing indefinitely Most importantly, it will be seen that extraction of the distillate up to raifinates of 65 or less viscosity index did not afiect the haze point appreciably. On the other hand, the ASTM cloud increased essentially linearly with viscosity index.

Figure 1 thus indicates that by controlling the degree of phenol extraction to yield a rafiinate having a viscosity index within a given range (viscosity index of less than 65), viscosity index properties can be at least partly brought up to commercial qualifications without adversely afiecting the propensities of the lube .to haze upon standmg.

The present invention makes use of the relationships depicted in Figure 1 in combination with the fact that hydro-isomerization has been found to be successful in further increasing the viscosity index of the rafiinate of the phenol extraction without deleteriously affecting the haze point.

The isomerization reaction may be carried out in the presence of various isomerization catalysts. Thus, one or more of the following catalytic materials may be used:

TABLE 1 Isomerization conditions Broad Preferred Range Range Temperature, F 600-800 650-750 Pressure, p.s.i.g -1, 000 100-400 Hydrogen Rate, Std. ftfi/bbl. of-feed 500-5, 000 500-1, 000

(Vol. liquid feed/hr.) Feed Rate, v./v./hr. 0. 1-10 0. 5-2.0

V01. of catalyst 1 Measured at 70 F., 1 atmosphere.

It is to be noted that the present hydro-isomerization step is clearly distinguished from destructive hydrogenation procedures heretofore known in the art for treating lubricants. Whereas destructive hydrogenation seeks to break up molecules under high pressure conditions and gives relatively low yields, the present hydrogen treatment promotes the branching of molecules, utilizes much less severe conditions and gives essentially 100% yield of isomerized product having a substantially increased viscosity index.

In accordance with the present invention, phenol extraction is limited in severity so as to give a rafiinate of .an intermediate viscosity index which falls in the range of constant "haze point, and this raflinate is then hydroisomerized to bring its viscosity index up to commercially desired levels without causing significant adverse effect upon its haze point.

With reference to Figure 2, a specific embodiment of the present invention will now be described. It is desired to produce a low cold test lube having a pour point of 0 F. or less and a viscosity index of at least 75.

As is conventional, the feed material for the phenol extraction step is derived by subjecting a crude, e.g. a naphthenic crude such as Tia Juana 102, to fractional distillation. As illustrated, the crude is fed to distillation unit 10 wherein it undergoes fractional distillation. Light naphtha constituents are taken overhead by line 16 while a heavy tar is withdrawn by line 14. Other fractions, such as gas oil, may be withdrawn by one or more lines 17. Recovered through outlet 15 for ultimate use as a lube product is a hydrocarbon fraction boiling in the range of 700 to 1100 F., and having the following range of properties: Viscosity index 35-45, pour point -l0 to +10 F., ASTM cloud point 5 to +10 F., and haze point 40-50 F. More detailed physical characterization is given in Table 2.

The distillate is passed to extraction zone 11 wherein it is contacted with phenol introduced into the upper portion of the extraction zone. Approximately 2 volumes of phenol are employed per volume of distillation feed. The phenol contains 5 vol. percent water. The extraction is carried out at 200 F. and yields a raflinate having a viscosity index within the range of constant haze point. In the present example, the degree of extraction is controlled to yield a raffinate having a viscosity index of 64 and consequently a haze point of about 45 F. The rafl-lnate, together with the distillate feed and isomerized product, are further characterized in Table 2.

A heavy extract portion is withdrawn from the extraction zone by line 19. In addition to phenol, the extract will contain single ring and condensed ring aromatics and sulfur compounds removed from the distillate fraction during the extraction step. The extract may be discarded, or as will later be described, partially used to stabilize the final high viscosity index product.

The rafiinate is withdrawn from the extraction zone by line 20 and passed to hydro-isomerization zone 12. Hydro-isomerization zone contains a fixed bed of isomerization catalyst and is adapted to isomerize the raifinate to more branched molecules. In the present example, the catalyst comprises 0.6 wt. percent platinum and 0.6 wt. percent chlorine on an alumina base. Catalyst pellets inch in diameter are employed. Isomerization zone 12 operates at a temperature of 700 F. and a pressure of 400 p.s.i.g. When employing a raffinate feed rate of 1 vol. liquid feed/vol. of catalyst/hr., approximately 500 standard cubic feet of hydrogen per barrel of feed is introduced into zone 12 by inlet 21. Gases are vented by line 23. Catalyst is withdrawn and replaced to maintain requisite catalytic activity by means of conduit 22.

The properties of the isomerized product passing through line 24 are tabulated below.

TABLE 2 Properties of feed, raffinate, and zsomerlzed product Distillate Raflinate Isomerlzed Feed Product Gravlty, API 21 25. 8 26. 7 lash, F 450 470 440 Color, 'l.R. (Tag Robinson). 17. 5 17. 25 Colorhold, T.R 16 17.25 Conradson Carbon, wt. percent. 0.02 0.01

Viscosity F., S.S.U. (Saybolt Seconds Universal). 950 536 436 Viscosity 210 F., S.S.U- 70 59. 3 57. 0 Viscosity Index 38 64 79 ASTIVI Cloud Point, F +2 38 40 Pour Point, F 5 15 -5 Haze Point, F 45 '45 50 Table 2 illustrates that hydro-isomerization served to substantially increase the viscosity index of the raffinate without severely affecting the haze point. If the phenol extraction had been run to yield a raffinate of as high a viscosity index, Le. 79, the haze temperature of the lube product would have been raised by approximately 25 F. In contrast, the present process results in only a negligible increase.

It is thus seen that the present combination of process steps successfully increased viscosity index and maintained pour point at commercially desired levels without causing a significant increased tendency towards haze formation in the final lube product as is characteristic of the prior art processes.

In a further refinement of the present invention, a portion of the extract may be blended with the isomerized product. In this embodiment, about 2-5 wt. percent extract based on isomerized product is blended with the high viscosity index product by means of line 25, the final blended product being withdrawn from the system by outlet 26. While the phenol extraction step does remove low viscosity index material, it also removes compounds, e.g. single ring and condensed ring aromatics, and sulfur compounds, which promote oxidation stability and serve as wax solubilizers.

Thus, by blending in small portions of the extract so that the final blend still has a high viscosity index, e.g. greater than 75, a more stable lube product is obtained. If desired, the extract portion to be blended may be subjected to hydrofining or hydro-isomerization to upgrade its properties prior to blending.

Numerous modifications may be made to the present invention without departing from the spirit thereof. The phenol extraction step may be a batch or continuous operation having a single stage or multiple stages. Various refining steps may be employed in conjunction with those described. For example, the raifinate of the phenol extraction zone may be clay treated prior to isomerization in order to upgrade the feed passed to the catalytic treating zone.

By use of the present combination process, a high viscosity index lube having good hazing properties is obtained in an eflicient and economically attractive manner.

What is claimed is:

1. An improved process for the manufacture of lube products from a hydrocarbon stream derived from a naphthenic crude which comprises extracting said hydrocarbon stream with phenol to increase the viscosity index of said hydrocarbon stream, recovering from said phenol extraction step a raflinate having about the same haze point as said hydrocarbon stream and isomerizing said raflinate in the presence of hydrogen to increase the viscosity index of said raflinate while preserving the haze point of said raflinate at substantially the same value.

2. The process of claim 1 wherein said raflinate has a viscosity index of less than about and the product from said isomerization step has a viscosity index of at least 75.

3. The process of claim 1 wherein the product from said isomerization step is a low cold test lube.

4. The process of claim 1 wherein a relatively small portion of the extract of said phenol extraction step is blended with the product from said isomerization step in order to serve as a wax solubilizer and to promote oxidation stability.

5. An improved method of producing high viscosity index cold test lubes from a hydrocarbon feed derived from a naphthenic crude, which comprises the steps of; extracting said hydrocarbon feed with phenol in an extraction zone so as to produce a raffinate having a viscosity index of less than about 65, said rafiinate viscosity index being within the range of viscosity indexes corresponding to substantially constant haze point; and subjecting said rafiinate to isomerization in the presence of hydrogen so as to increase its viscosity index to at least about while preserving its haze point substantially constant.

6. The improved method of claim 5 wherein the ultimate lube product of the improved method has a maximum pour point of 0 F.

7. The improved method of claim 5 wherein a portion of the extract of said extraction zone is blended With the isomerized lube product so as to act as an anti-oxidant and wax solubilizer, the blended extract portion comprising less than 5 wt. percent of said lube product.

8. The improved method of claim 5 wherein said rafiinate is subjected to isomerization at about 650 to 750 F. and at a pressure of about to 400 p.s.i.g.

9. An improved process for producing low cold test lubes from a hydrocarbon fraction derived from a naphthenic crude source which comprises; extracting said hydrocarbon fraction with phenol in an extraction zone for a time sufficient to yield a raffinate characterized by a viscosity index of less than about 65, the viscosity index of said raflinate falling within the range of substantially constant haze point; thereafter subjecting said rafiinate to isomerization in the presence of hydrogen and an isomerization catalyst so as to produce a lube having a pour point of at most 0 F., and having a viscosity index of at least about 75 while preserving said haze point substantially constant.

References Cited in the file of this patent UNITED STATES PATENTS 2,247,475 Bray July 1, 1941 2,668,790 Good Feb. 9, 1954 2,668,866 Good Feb. 9, 1954 2,773,005 Meyer et a1 Dec. 4, 1956 FOREIGN PATENTS 748,154 Great Britain Apr. 25, 1956 

1. AN IMPROVED PROCESS FOR THE MANUFACTURE OF LUBE PRODUCTS FROM A HYDROCARBON STREAM DERIVED FROM A NAPHTHENIC CRUDE WHICH COMPRISES EXTRACTING SAID HYDROCARBON STREAM WITH PHENOL TO INCREASE THE VISCOSITY INDEX OF SAID HYDROCARBON STREAM, RECOVERING FROM SAID PHENOL EXTRACTION STEP A RAFFINATE HAVING ABOUT THE SAME HAZE POINT AS SAID HYDROCARBON STREAM AND ISOMERIZING SAID RAFFINATE IN THE PRESENCE OF HYDROGEN TO INCREASE THE VISCOSITY INDEX OF SAID RAFFINATE WHILE PRESERVING THE HAZE POINT OF SAID RAFFINATE AT SUBSTANTIALLY THE SAME VALUE. 